RP7- Determining Rate Equations Flashcards
What two experiments can be used to determine the order of reactants
The initial rates method
The continuous monitoring method
Describe what the initial rates method is
Where the rate of reaction at the very start of the reaction is measured
Carry out an experiment with all the reactants, each time choose a specific reactant to change the concentration, and the others should be in excess so they are effectively constant.
Measure the time taken for a specific colour change, and plot a graph with 1/t (rate) against concentration
The gradient of this graph can be used to determine if it is 0 1 or 2 order
What will be seen on a concentration rate graph for a 0 1 and 2 order reactant?
0- the change in conc. has no effect on the rate. Straight line with no gradient
1- straight line through the origin shows that the rate is directly proportional to the conc.
2- curved gradient shows the rate is proportional to the change in conc. squared
What is quenching? How can this be done?
When a reaction is stopped at a specific time, so a titration can be carried out and the conc. can be determined
- cool it rapidly in an ice bath
- dilute the solution with lost of water
- add a quenching agent that can remove an acid catalyst
Describe the continuous monitoring method
Measures the conc. of a reactants or products throughout the reaction to see how they change.
Perform the reaction, and measure the amount of substance at regular timed intervals. Plot this on a conc. time graph and see how the gradient (rate of reaction) changes
During the continuous monitoring method, what sort of changes can be monitored over the reaction?
pH
Volume of gas produced
Colour using a colorimeter
Mass loss if a gas is produces=d and allowed to escape
